Gyroids

A gyroid is a gyrating clay figurine. Gyroids make an appearance in all of the Animal Crossing games. Most types act like furniture, but some in the first Animal Crossing are interactive. There are many different types of gyroids, such as bowtoids and freakoids, and they also come in different shapes and sizes such as mini, big, squat, and tall. They can be dug up and placed inside your house to add character or play music. Each gyroid makes a different sound, and when many are put together, you can create your own gyroid symphony. Gyroids will also play faster or slower depending on the music playing.

When you walk around town, you sometimes see a star shaped crack in the ground. That means that there is something buried under the ground. With a shovel, you can dig them up. Most of the time, you will either dig up a gyroid or a fossil. There's also a few pitfall seeds as well. You can find up to as many as three gyroids in the ground each day.

There is always one gyroid outside of your house, and outside of the other three houses in the main square. This is where you must save your game after you have finished playing. You can also change the door pattern, set welcome messages, or put up items for sale by talking with your gyroid with the A button. These are the only gyroids that are capable of speech. All others simply make noise.

In Animal Crossing: Wild World, the gyroid near your house is now gone. Gyroids will serve a different purpose in this game. You can now go around looking for cracks in the dirt. If you happen to see one of these in the ground, dig it up with your shovel and it may be a gyroid, a Fossil, or a Pitfall seed. Gyroids have no purpose except to place them in your house for decoration or sell them to Nook for 828 Bells each.

In Animal Crossing: City Folk, gyroids have made a return. They serve the exact same role that they did in Animal Crossing: Wild World. Gyroids can be dug up from small cracks in the dirt, often after rainy days. These can be used like furniture inside your house. When they are placed, they will start making noises. To stop or start them, press the A button. However, there is a new feature including them. This time, if you collect them, Brewster will open up a secret storage space for gyroids once you drink seven cups of coffee in a row while it is hot. A few new gyroids have been added to the game this time around. Also, a gyroid named Lloid now runs the Auction House.

Gyroids play pretty much the same role in the 3DS version of Animal Crossing, as they did in the DS version.
Primarily just furniture with no purpose other than to make noise in your house, there is a talking Gyroid called Lloid who takes donations for public projects - which coincidentally is they only way to get them built.